The present invention relates to a connector element for optical fiber.
In the present invention the term xe2x80x9cferrulexe2x80x9d is used, as it is by specialists in the field, to designate a cylindrical sheath provided with a central channel serving to receive the stripped end portion of an optical fiber so as to hold it accurately in alignment with another optical fiber held by the ferrule of another connector element.
It is known that putting in place connector elements at the ends of optical fibers requires difficult and often lengthy handling operations, and the quality of the optical transmission between the fibers connected in that way depends on those handling operations being performed properly.
Among the required operations, there is one that requires particular care because it can not only degrade the quality of the optical connection, but it can also damage the connector. The operation in question is that of gluing the stripped optical fiber inside the ferrule of the connector.
In order to perform that operation, a syringe is inserted into the connector via the rear end thereof, to the mouth of the central channel of the ferrule, so as to deposit a drop of glue therein.
Once the drop of glue has been deposited, it is necessary to extract the syringe from the connector element without soiling the inside of said element, while a drop of glue is projecting from the end of the syringe.
The difficulty consists in withdrawing the syringe while holding it accurately oil the axis of the connector element, so that it does not touch any portion of the connector element.
Unfortunately, the few millimeters of diameter of the orifice via which rho syringe is inserted and then withdrawn make it almost impossible to withdraw the syringe manually without it touching the walls of said orifice. Automating that operation is justified only for large quantities of cabling in the factory and it does not solve the problem of cabling on the site on which the fiber is used, special tools being required for such in situ cabling.
An object of the present invention is to provide a solution to that particular problem of extracting the syringe without soiling the inside of the connector element.
The present invention provides a connector element for optical fiber, said connector element comprising:
a ferrule serving to hold a stripped end portion of an optical fiber;
an elongate ferrule support having a front end suitable for supporting the ferrule, a rear end opposite from the front end, and a channel extending from the rear end to the front end and via which the non-stripped portion of the optical fiber can pass through said support so that the stripped end portion of the fiber can be engaged in the ferrule; and
a body inside which the ferrule and its support are received, said body having a front end for connecting the connector element to another connector element, and a rear end via which the optical fiber penetrates for the purpose of engaging in the ferrule support and then in the ferrule, said rear end extending beyond the rear end of the ferrule support, when the connector is in the assembled state;
said connector element being characterized by the fact that, in its rear portion, the body is provided with a cylindrical portion which preferably has a crenelated outside wall and around which a crimp sleeve engages, and with a notch extending from the rear end of the body so as to provide unobstructed radial access to the ferrule support.
The notch provided in the wall of the rear end of the body makes it possible for the syringe to be released from the ferrule support directly Lo the outside of the connector element without touching any other piece of said connector element.
Thus, the syringe is guided along the entire length of its exit path through the ferrule support which can enter into contact: with the drop of glue projecting form the syringe without that having any adverse effects, since the non-stripped optical fiber is to be glued inside the ferrule support. As soon as it exits from the ferrule support, the syringe leaves the connector element without soiling the rear end of the body thereof.
In order to facilitate the release of the syringe, provision is preferably made for the notch to be wider than the rear end of the ferrule support.
In a preferred embodiment of the invention, the notch is substantially U-shaped, the middle axis of the U-shape being parallel to the longitudinal axis of the ferrule support.
Advantageously, the ferrule support is a piece that is substantially circularly symmetrical, as is known, and the body is a piece that is internally circularly symmetrical and coaxial with the ferrule support.
For the purpose of further facilitating the release of the syringe at the outlet of the body of the connector element, each branch of the U-shape of the notch is cut out in the thickness of the wall of the body in a respective plane, arid the two planes corresponding to respective ones of the branches of the U-shape forming an angle xcex8 between them of about 20xc2x0 and offering an opening that subtends an angle of about 40xc2x0 on the axis of the body.
In a particular embodiment of the invention, the connector element further includes a structure for reinforcing the rear end of the body, in the form of a piece, shaped to fit into said body via the rear end thereof so as to support the wall of said body around the notch.
This reinforcing structure supports the wall of the body at its rear end, where it is weakened by the presence of the notch.
The configuration of the invention for the cylindrical rear portion of the connector element and for the crimp sleeve that surrounds it constitutes securing means for securing the strength members of an optical cable including the optical fiber to the connector element so as to prevent the ferrule and its support from being subjected to any traction that is exerted on the optical cable.
In a preferred variant, the securing means also secure the outer covering of the optical cable to the body of the connector element so as to prevent the ferrule and its support from being subjected to any traction that is exerted on the optical cable.
In a preferred version of this embodiment, the securing means further include an anvil, the anvil being a circularly-symmetrical piece engaged under the wall of the body of the connector element and around the stripped optical fiber, the crimp sleeve undergoing plastic deformation by being crushed, thereby holding the strength members captive against the wall of the body that is supported by the anvil.
In a particular embodiment, the reinforcing structure and the anvil are constituted by a single piece.
In this embodiment, it may he advantageous for the anvil to extend the outside wall of the body of the connector element rearwards, thereby increasing the length over which the strength members are crimped, without lengthening the connector element.
In addition, the anvil may be provided with a rear segment of smaller diameter organized to enrage under the covering of the cable, the inside of the crimp sleeve being provided with a constriction of corresponding diameter, so that, on crimping the strength members, the covering of the cable is simultaneously secured to the anvil.
In a particular embodiment of the invention, a cable support sleeve is that is resiliently flexible is provided at the rear of the connector element and serves to guide the optical cable while preventing it from kinking as it leads out from the connector element.
In a variant of this embodiment, the cable support sleeve is engaged on the crimp sleeve, and the crimp sleeve extends towards the rear of the connector beyond the anvil where it is provided with a flared mouth offering radial clearance to the optical cable so that when the cable support sleeve is subjected to bending and moves the optical cable off axis relative to the connector element, said cable support sleeve bears against the crimp sleeve, and so that the distance between the rear end of the anvil and the rear end of the crimp sleeve makes it possible for the optical cable, whose axis coincides with the axis of the connector element at the rear outlet of the anvil, to bend progressively so as to lie on the axis of the cable support sleeve at the outlet of the crimp sleeve.
More generally, in its rear portion, the crimp sleeve acts as a spreader by holding the support sleeve at a distance from the cable when said sleeve deforms, so as to conserve radial and axial clearance around the cable to enable it to move off-axis without being sheared.
In other words, at the rear of the connector element, the cable support sleeve bears against a cylindrical spreader having a flared mouth and that extends to the rear of the connector element around and beyond any securing means for securing the cable.
Preferably, that end of the cable support sleeve which is opposite from body of the connector element is provided with a flared mouth enabling the optical cable leading out from said outlet sleeve to take up a curvature compatible with the minimum radius of curvature of the optical fiber.